Bottom Line:
We demonstrated one-step method to fabricate two different sizes of graphene quantum dots (GQDs) through chemical cutting from graphene oxide (GO), which had many advantages in terms of simple process, low cost, and large scale in manufacturing with higher production yield comparing to the reported methods.Bright blue luminescent GQDs were obtained with a produced yield as high as 34.8%.Moreover, how the different sizes affect fluorescence wavelength mechanism was investigated in details.

ABSTRACTWe demonstrated one-step method to fabricate two different sizes of graphene quantum dots (GQDs) through chemical cutting from graphene oxide (GO), which had many advantages in terms of simple process, low cost, and large scale in manufacturing with higher production yield comparing to the reported methods. Several analytical methods were employed to characterize the composition and morphology of the resultants. Bright blue luminescent GQDs were obtained with a produced yield as high as 34.8%. Moreover, how the different sizes affect fluorescence wavelength mechanism was investigated in details.

Mentions:
To further confirm the functional groups on the surface of the as-prepared GQDs-1 and GQDs-2, X-ray photoelectron spectroscopy (XPS) characterization was carried out. Figure 6a showed the XPS spectrum of C1s of GO as preparation GQDs precursor. The measured spectrum can be deconvoluted into five surface components, corresponding to sp2 (C = C) at a binding energy of 284.5 eV, sp3 (C–C and C–H) at 285.5 eV, C–OH at 286.8 eV, C–O–C at 287.2 eV as well as C = O or COOH at 288.4 eV. It should be noted that the XPS data presented here represent the surface components of the GO. The surface components of the GQDs as determined by the XPS data were in good agreement with FT-IR results. Figure 6b, c showed the XPS spectra of GQDs-1 and GQDs-2. The GQDs-1 spectrum showed peaks at 284.5, 286.3, 287.8, and 288.4 eV, which corresponded to SP2C (C = C) or SP3C (C–C, C–H), C–OH, C = O, and COOH chemical binding states, respectively. The XPS spectra of C = O and COOH peaks of GQDs-1 related to GQDs-2 become visibly weakened. This indicated the occurrence of an acid oxidation by H2SO4/KMnO4 second oxidation mechanism that helped to cut the GO into the containing C = O of the edge of GQDs-2. The signal of GQDs-2 at 284 eV assigned to carboxyl groups became weak, whereas the sp2 carbon peak at 284.5 eV was almost unchanged. The deoxidization was further confirmed by the changes in the FT-IR and C1s XPS spectra.Figure 6

Mentions:
To further confirm the functional groups on the surface of the as-prepared GQDs-1 and GQDs-2, X-ray photoelectron spectroscopy (XPS) characterization was carried out. Figure 6a showed the XPS spectrum of C1s of GO as preparation GQDs precursor. The measured spectrum can be deconvoluted into five surface components, corresponding to sp2 (C = C) at a binding energy of 284.5 eV, sp3 (C–C and C–H) at 285.5 eV, C–OH at 286.8 eV, C–O–C at 287.2 eV as well as C = O or COOH at 288.4 eV. It should be noted that the XPS data presented here represent the surface components of the GO. The surface components of the GQDs as determined by the XPS data were in good agreement with FT-IR results. Figure 6b, c showed the XPS spectra of GQDs-1 and GQDs-2. The GQDs-1 spectrum showed peaks at 284.5, 286.3, 287.8, and 288.4 eV, which corresponded to SP2C (C = C) or SP3C (C–C, C–H), C–OH, C = O, and COOH chemical binding states, respectively. The XPS spectra of C = O and COOH peaks of GQDs-1 related to GQDs-2 become visibly weakened. This indicated the occurrence of an acid oxidation by H2SO4/KMnO4 second oxidation mechanism that helped to cut the GO into the containing C = O of the edge of GQDs-2. The signal of GQDs-2 at 284 eV assigned to carboxyl groups became weak, whereas the sp2 carbon peak at 284.5 eV was almost unchanged. The deoxidization was further confirmed by the changes in the FT-IR and C1s XPS spectra.Figure 6

Bottom Line:
We demonstrated one-step method to fabricate two different sizes of graphene quantum dots (GQDs) through chemical cutting from graphene oxide (GO), which had many advantages in terms of simple process, low cost, and large scale in manufacturing with higher production yield comparing to the reported methods.Bright blue luminescent GQDs were obtained with a produced yield as high as 34.8%.Moreover, how the different sizes affect fluorescence wavelength mechanism was investigated in details.

ABSTRACTWe demonstrated one-step method to fabricate two different sizes of graphene quantum dots (GQDs) through chemical cutting from graphene oxide (GO), which had many advantages in terms of simple process, low cost, and large scale in manufacturing with higher production yield comparing to the reported methods. Several analytical methods were employed to characterize the composition and morphology of the resultants. Bright blue luminescent GQDs were obtained with a produced yield as high as 34.8%. Moreover, how the different sizes affect fluorescence wavelength mechanism was investigated in details.